A combined device of this type is unknown in the textile technology. The drawing frame as a textile machine for the doubling and drafting of several fiber assemblies to form one sliver is known. Slubbing machines for the manufacture of what are known as roving yarns from one or more slivers are indeed also known. However, stubbing machines with twist application elements according to the present invention are unknown. The stubbing machines according to the present invention include, for example, the speed frame or roving frame. The roving yarn serves as the supply material for the actual spinning process. For example, the roving yarn may serve as the supply material for the spinning of the fibers to make a fiber yarn on a ring-spinning machine.
The fiber assemblies coming from the preliminary system (carding room) are, according to the prior art, first doubled with the aid of drawing frames and at the same time stretched or drafted, and then deposited in cans. The sliver which results from this process is then supplied to the stubbing machines (speed frames) for further processing. The sliver is first subjected to further stretching or drafting in an individual drafting assembly. Second, the sliver is slightly twisted by the application of twist. The original fiber assembly is then wound up as roving yarn on a roving yarn bobbin. The roving yarn, also referred to as fiber stubbing, flyer stubbing, flyer yarn or generally slubbing, usually serves as supply material for ring-spinning machines.
The slubbing machine, as mentioned, usually exhibits its own drafting device. In most cases, this drafting device is a double apron draft system. After being drawn through the drafting device of the slubbing machine, the fiber assembly undergoes a slight twist, referred to as a protective twist, in order for the slubbing to exhibit sufficient strength to be wound on a bobbin without disintegrating. The twist must only be of sufficient strength for the roving yarn to be held together for the winding and later unwinding and for the transport of the bobbins. In particular, the twist must be sufficiently strong to prevent false drafts (thin places in the roving yarn) from occurring. The twist must be easy to release and the roving yarn must be capable of being drawn for the subsequent spinning process, for example in a ring-spinning machine, to be put into effect.
A speed frame is often used as a slubbing machine to manufacture the correspondingly-named flyer stubbing. The speed frame is equipped with a drafting device and a spindle for winding up the flyer stubbing onto a cylinder bobbin by means of a flyer which supports the slubbing against the centrifugal force incurred by the bobbin revolutions. The speed frame is an expensive machine due to the complicated winding mechanism. In addition, the usual output from a speed frame is about 20-25 meters of roving yarn per minute. This low production cannot be increased with regard to the winding system with flyers because a higher speed is limited by the centrifugal force that the flyers and roving yarn bobbin must withstand.
Attempts have been made to circumvent the use of the stubbing machine by a process called direct spinning or sliver-to-yarn spinning. In this process, the sliver is delivered directly as supply material for the ring-spinning machine. However, the high draft produced by sliver direct spinning only achieves the result to a restricted degree compared to that obtained with the supply of a flyer slubbing on the ring spinning machine. This is particularly true if fine yarns with Nm 50 and finer are being spun. In addition, the supply of drafting cans with fiber slivers to ring-spinning machines is elaborate and complicated.
One possibility for replacing a speed frame is disclosed in the printed specification EP 375 242 A2. This publication describes a machine for the manufacture of a roving yarn from a fiber assembly having a twist application means with a rotating rotor. The rotor exhibits a continuous longitudinal hole on its axis of rotation through which the fiber assembly to be twisted is guided. The rotor has at a specific height several holes arranged rotationally symmetrically in the radial direction. These radial holes connect the longitudinal hole with the outer surface of the rotor. This outer surface of the rotor is subjected to a vacuum or a strong under-pressure. As the fiber assembly is drawn through the longitudinal hole, individual free fiber ends are sucked off the surface of the fiber assembly into the radial holes. In operation, the rotor rotates while the fiber assembly is drawn through the longitudinal hole. In this manner, the fiber ends located in the radial holes are wound around the moving fiber assembly. As a result, a true twist is applied to the fiber assembly or its individual fibers. The device according to the above mentioned publication is relatively expensive in manufacture and operation due to the mechanical elements (rotating rotor) and the vacuum technology.
DE 32 37 989 C2 teaches the principle of drawing a fiber stubbing or drawing sliver in a drafting device and then applying a twist to the drawn fiber assembly. The application of the twist is effected by air jets in two sequential twist chambers. The application of the twist in the first pneumatic twist chamber is performed in a direction counter to the application of twist in the second pneumatic twist chamber. For example, the first twist application causes, a left-hand rotation and the following twist application in the second twist chamber causes a right-hand rotation. A yarn produced in this manner is produced in accordance with what is known as a false twist spinning process.
Patent Specification CH 617 465 teaches a false twist nozzle used for the manufacture of a staple fiber yarn, which likewise utilizes a false twist spinning process. During the production of a yarn, i.e. during the spinning process, the individual fibers are spun or twisted with one another sufficiently strongly for the twisting to be quasi-irreversible, and the yarn produced cannot be drawn any further. The strengthening achieved by the twisting is necessary because it is the only way it will obtain the necessary high tensile strength. The consequence of this, however, is that the devices and spinning processes referred to are not suitable for forming a roving yarn. A roving yarn exhibits only what is referred to as a protective twist. A protective twist must not impede the further spinning processes on the following machines, for example drafting at the ring-spinning machines. In other words, roving yarn must remain capable of being drawn or drafted. The devices described in the two publications above are therefore only suitable for the manufacture of yarns and are not suitable for the manufacture of a roving yarn that remains capable of being drafted.
An object of the present invention is to provide a drawing frame-slubbing machine combination and a method for the manufacture of a roving yarn that avoids the disadvantages referred to above and exhibits the characteristics of conventional flyer slubbings or roving yarns.